netdev - Re: [BUG] powerpc does not save msi state [was Re: [PATCH 5/7] pci: Export the pci_restore_msi

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Date:	Mon, 22 Oct 2007 14:54:52 -0500
From:	linas@...tin.ibm.com (Linas Vepstas)
To:	David Miller <davem@...emloft.net>
Cc:	linuxppc-dev@...abs.org, mchan@...adcom.com, mcarlson@...adcom.com,
	netdev@...r.kernel.org, linux-pci@...ey.karlin.mff.cuni.cz,
	michael@...erman.id.au
Subject: Re: [BUG] powerpc does not save msi state [was Re: [PATCH 5/7] pci: Export the pci_restore_msi_state() function

On Fri, Oct 19, 2007 at 05:53:08PM -0700, David Miller wrote:
> From: linas@...tin.ibm.com (Linas Vepstas)
> Date: Fri, 19 Oct 2007 19:46:10 -0500
> 
> > FWIW, it looks like not all that many arches do this; the output
> > for grep -r address_hi * is pretty thin. Then, looking at
> > i386/kernel/io_apic.c as an example, one can see that the 
> > msi state save happens "by accident" if CONFIG_SMP is enabled;
> > and so its surely broekn on uniprocesor machines.
> 
> I don't see this, in all cases write_msi_msg() will transfer
> the given "*msg" to entry->msg by this assignment in
> drivers/pci/msi.c:
> 
> void write_msi_msg(unsigned int irq, struct msi_msg *msg)
> {
>  ...
> 	entry->msg = *msg;
> }
> 
> So as long as write_msi_msg() is invoked, it will be saved
> properly.

As Michael Ellerman points out, the pseries msi setup is done
by firmware, and so this bit never happens. 

As discussed in the other thread, I'll try to set up a patch
for an arch callback for restoring msi state.

-linas
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